1. Field of the Invention
The present invention relates to a Fresnel lens type complex reflection system.
2. Description of the Prior Art
An ordinary method of converging and diverging a light is to either use a paraboidal mirror (generally referred to as a conicoidal mirror) or a lens.
However, these methods have the following problems:
First, regarding the former method,
(1) if planning to make a large caliber reflecting mirror, either the focal length will need to be long or the depth of the mirror will need to be great, and thereby the whole size of the mirror will increase greatly, and
(2) if considering a case in which the light converged at a focal point is utilized, a means for taking out and utilizing the light is a hindrance to an incident ray since both the incident ray and the focal point are on the same side of the mirror.
This is the same also in case the direction of light is opposite.
And on the latter method,
(3) the range of wave-lengths utilizable is narrow since the refraction of an incident ray in a solid medium is utilized;
(4) the method cannot be used for this same reason since the medium is broken when the strength of light is too high; and
(5) it is difficult to avoid the chromatic aberration which results from utilizing the refraction of an incident ray.